The value of capillary electrophoresis as a separation and analytical technique has been recognized for some time. In capillary electrophoresis, a small tube or capillary is filled with an electrically conductive fluid, or buffer. A small quantity of a sample to be analyzed is introduced into one end of the capillary bore, the ends of the capillary are placed into separate reservoirs of buffer, and a direct current high voltage is applied to the ends of the capillary by means of electrodes positioned in the buffer reservoirs, causing a small current to flow through the capillary.
With the correct polarity applied across the capillary, the sample begins to migrate toward the other end of the capillary and the buffer begins to migrate the opposite direction. As this migration occurs, different molecules in the sample travel at different rates, causing the sample to become separated into bands of these different molecules. These bands or groups of different molecules are detected near the other end of the capillary by, for example, passing a perpendicular light beam through the bore of the capillary. Changes to the light beam, such as absorbance caused by the different molecules, are detected as the separated molecules pass through the beam, thus identifying the different molecules or the classes or categories of molecules in the sample and the relative concentration of such molecules.
To make the technique easier to use and less labor intensive, several efforts have been made to automate the analysis of samples in capillary electrophoresis systems. For example European Patent Application number 89302489.3, publication number 0,339,779 A2, corresponding to U.S. patent application Ser. No. 188,773, filed Apr. 29, 1988 now abandoned (Burolla) describes an automated capillary electrophoresis apparatus. That apparatus includes two conveyors for positioning vials under ends of a capillary mounted in a cartridge. The ends of the capillaries along with electrodes are inserted into the vials by means of hypodermics that pierce caps on the vials. A single detector provides detection of the electrophoresed sample.
Automated capillary electrophoresis apparatus is described in U.S. Pat. No. 5,045,172 to Guzman. The Guzman apparatus includes two rotating tables at opposite ends of the apparatus that hold sample and buffer cups. A capillary, which is described in Guzman as being a single capillary or a plurality of capillary tubes operated in parallel or in a bundle, has two opposite ends. These ends are positioned by automated arms and posts in respective corresponding pairs of cups to first draw sample into the capillary and to then electrophorese the sample. As with Burolla, a single detector is used to detect the results.
Both of these automated analyzers just described, however, present drawbacks with respect to sample handling. For example, each of such analyzers requires considerable manual manipulation despite their automated nature, such as preparing and placing individual sample and buffer vials onto the analyzer, programming the analyzer for the various analytical routines, and the like. Because only one sample can be electrophoresed and detected during each analysis cycle of the analyzers, the number of samples per unit timer or throughput, is severely restricted as compared to the needs of, for example, most routine clinical laboratory work.
A characteristic of prior art automated analyzers is that such analyzers often use multiple automated pipettes and turntables to move samples from a sample input area through the automated analysis cycle. Such an analyzer, for example, is disclosed in U.S. Pat. No. 4,908,320. Although such analyzers can achieve considerable throughput, the analyzers can be expensive and are often relatively large, floor-standing units.
Thus, there is a need for a sample handling system suitable for use, for example, in an automated capillary electrophoresis analyzer, that increases potential throughput of the analyzer yet is easy and relatively inexpensive to maintain. There is also a need for such a system that enables the analyzer to be relatively compact with few automated handling devices that can otherwise increase cost and size.